adventofcode2022/day17/sol.py

import itertools
rocks = [
    0b00011110,
    0b00001000_00011100_00001000,
    0b00000100_00000100_00011100,
    0b00010000_00010000_00010000_00010000,
    0b00011000_00011000,
]

jets = ">>><<><>><<<>><>>><<<>>><<<><<<>><>><<>>"

jets = open("input").read().strip()

rocki = itertools.cycle(rocks)

a = 0b11111111
wall = 0b10000000_10000000_10000000_10000000_10000000
stopped = 0
r = 0

def drop(a, r, jets):
    # start falling
    h = a.bit_length() + 8*3
    if h % 8 != 0:
        h += 8 - h%8
    numjets = 0
    while True:
        j = next(jets)
        if j == '<':
            x = (r<<1)
            if x & wall == 0:
                if x & (a>>h) == 0:
                    r = x
        elif j == '>':
            x = (r<<7)
            if x & wall == 0:
                x >>= 8
                if x & (a>>h) == 0:
                    r = x
        numjets += 1

        # continue falling?
        if r & (a>>(h-8)) == 0:
            h -= 8
            assert h > 0
        else:
            # stop
            a |= (r<<h)
            return a, numjets


a = 0b11111111
wall = 0b10000000_10000000_10000000_10000000_10000000
stopped = 0
jeti = itertools.cycle(jets)
i = 0
j = 0
seen = dict()
def head(a):
    h = a.bit_length()
    h -= h % 8
    x = (a>>h)&0xff
    while h >= 8 and x != 0x7f:
        h -= 8
        x |= (a>>h)&0xff
    if x == 0x7f:
        return a>>h
    return 0
import math
def height(a):
    return math.ceil(a.bit_length()/8)
try:
    while True:
        r = next(rocki)
        a, n = drop(a,r,jeti)
        stopped += 1
        i = (i+1) % len(rocks)
        j = (j+n) % len(jets)
        if (i,j,head(a)) in seen:
            break
        seen[(i,j,head(a))] = (a,stopped)
        #for i in reversed(range(0,a.bit_length(),8)):
        #    print("{:08b}".format((a>>i)&0xff))
        #print()
    b, old = seen[(i,j,head(a))]
    sdiff = stopped - old
    hdiff = height(a) - height(b)
    goal = 1000000000000
    rounds, extra = divmod(goal - stopped, sdiff)
    h = rounds*hdiff
    for _ in range(extra):
        r = next(rocki)
        a, n = drop(a,r,jeti)
    print(rounds*hdiff + height(a)-1)
finally:
    print(i, j, stopped)

print(math.ceil((a>>8).bit_length()/8))